Coolant containing organopolysiloxanes

Abstract

To provide organopolysiloxanes which retain flowability even at low temperatures and have a high flash point and which are suitable for use as a coolant for cooling devices having a mechanism for forcedly circulating the coolant.SOLUTION: This coolant includes linear organopolysiloxanes represented by formula (1) (wherein R1 moieties are each independently a methyl group or a hydroxyl group, and n is an integer of 1-30), wherein the content of the linear organopolysiloxanes represented by formula (1) in which n is 5 or smaller is 15 mass% or less with respect to the total mass of all the linear organopolysiloxanes, and the content of the linear organopolysiloxanes represented by formula (1) in which n is 16 or greater is 5 mass% or less with respect to the total mass of all the linear organopolysiloxanes.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a refrigerant containing an organopolysiloxane, and more particularly to a refrigerant for use in a cooling device having a mechanism for forced circulation of the refrigerant. [Background technology]

[0002] Cooling systems that use forced circulation pumps or other devices to circulate refrigerants have a wide range of applications, including cooling electronic devices, heat exchange in manufacturing plants, and air conditioning. Operating temperatures range from approximately -60°C to 150°C. Known refrigerant oils include mineral oils, alcohols, and halogenated hydrocarbons. Mineral oils become highly viscous at low temperatures, placing a heavy load on the circulating pump, while alcohols pose problems due to their toxicity and flammability. Among halogenated hydrocarbons, chlorinated hydrocarbons are regulated due to their contribution to global warming. For these reasons, fluorocarbons, which have low viscosity and low flammability even at low temperatures, have been widely used as refrigerant oils. However, the persistence of fluorocarbons has become a concern in recent years, and restrictions on their use are being considered.

[0003] Given these circumstances, there is a demand for alternative refrigerants to fluorocarbons, and silicone oils, which maintain fluidity even at low temperatures, have attracted attention. The use of silicone oils as refrigerants has been investigated in the past (Patent Document 1). However, the specification stipulated that a flash point of 60°C or higher would be sufficient, but this standard is insufficient in light of Japan's Fire Service Act and other regulations. Mixtures of decamethyltetrasiloxane and hexamethyldisiloxane have also been proposed, but these have low fluidity at low temperatures but high volatility and flash points below 100°C (Patent Document 2). Refrigerants primarily composed of siloxane oligomers have also been proposed, but they also have excellent fluidity at low temperatures but a low flash point (Patent Document 3). The development of alternatives to fluorocarbons for refrigeration applications is an urgent issue, and there is a need for refrigerants that maintain fluidity at low temperatures and have a high flash point. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 07-166061 [Patent Document 2] Japanese Patent Application Publication No. 02-242878 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-262168 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide an organopolysiloxane that maintains fluidity even at low temperatures, has a high flash point, and is suitable as a refrigerant for use in cooling devices having a mechanism for forced refrigerant circulation. [Means for solving the problem]

[0006] The present inventors have discovered that organopolysiloxanes containing reduced amounts of low-molecular-weight components and high-molecular-weight components exhibit fluidity at low temperatures while also having a high flash point, making them suitable as refrigerants.

[0007] That is, the present invention is [1] A refrigerant containing a linear organopolysiloxane represented by the following formula (1): [ka] (where R 1 are each independently a methyl group or a hydroxyl group, and n is an integer of 1 to 30. the amount of the linear organopolysiloxane represented by formula (1) in which n is 5 or less is 15 mass% or less based on the total mass of the linear organopolysiloxane; the amount of the linear organopolysiloxane represented by formula (1) in which n is 16 or more is 5 mass% or less based on the total mass of the linear organopolysiloxane; and, The refrigerant contains the following formula (2): [ka] (where m is an integer between 3 and 6) The amount of the cyclic polysiloxane represented by the formula (I) is less than 1 part by mass per 100 parts by mass of the linear organopolysiloxane. The refrigerant is provided.

[0008] Furthermore, the present invention provides the above refrigerant, which further has at least one component selected from the following: [2] The above refrigerant, wherein the amount of the linear organopolysiloxane represented by the formula (1) where n is an integer of 6 to 15 exceeds 80 mass % based on the total mass of the linear organopolysiloxane. [3] The above refrigerant, wherein the linear organopolysiloxane has a flash point of 150°C or higher. [4] The linear organopolysiloxane has a flash point of 150°C or higher and a kinematic viscosity of 100mm at -60°C. 2 The above refrigerant having: [5] The above refrigerant, which is a refrigerant for a cooling device. [6] The above refrigerant, wherein the cooling device has a mechanism for forced circulation of the refrigerant.

[0009] More preferably, the present invention provides a refrigerant comprising a linear organopolysiloxane represented by formula (1) above, wherein the amount of linear organopolysiloxanes represented by formula (1) above where n is 5 or less contained in the refrigerant is 15 mass% or less, based on the total amount of linear organopolysiloxanes; the amount of linear organopolysiloxanes represented by formula (1) above where n is 16 or more contained in the refrigerant is 5 mass% or less, based on the total amount of linear organopolysiloxanes; and the amount of cyclic polysiloxanes represented by formula (2) above associated with the linear organopolysiloxane represented by formula (1) above is less than 1 part by mass per 100 parts by mass of the linear organopolysiloxane. [Effects of the Invention]

[0010] The linear organopolysiloxane of the present invention maintains good fluidity at low temperatures and has a high flash point, making it usable as a refrigerant over a wide temperature range. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention is a refrigerant containing a linear organopolysiloxane represented by the following formula (1). [ka] (where R 1 are each independently a methyl group or a hydroxyl group, and n is an integer of 1 to 30.

[0012] In the above formula (1), R 1 are each independently a methyl group or a hydroxyl group, and preferably a methyl group. n is an integer of 1 to 30, and preferably an integer of 1 to 20. The main component of the linear organopolysiloxane contained in the refrigerant of the present invention is a linear organopolysiloxane represented by the above formula (1) where n is an integer of 6 to 15. The linear organopolysiloxane is contained in an amount of more than 80 mass %, preferably 85 mass % or more, more preferably 90 mass % or more, and even more preferably 95 mass % or more, based on the total mass of the linear organopolysiloxane.

[0013] In the present invention, the amount of linear organopolysiloxanes represented by the above formula (1) where n is 5 or less contained in the refrigerant is 15% by mass or less, preferably 10% by mass or less, and more preferably 5% by mass or less, based on the total amount of linear organopolysiloxanes. If the amount of linear organopolysiloxanes where n is 5 or less exceeds the upper limit, the fluidity of the refrigerant at low temperatures will be improved, but this is undesirable because the flash point will be lowered. There is no particular restriction on the lower limit, and the closer to 0% by mass the better, but for example, it is 0.01% by mass or more, preferably 0.1% by mass or more. 0% by mass is particularly preferred. Furthermore, in the present invention, the amount of linear organopolysiloxanes represented by the above formula (1) in which n is 16 or greater contained in the refrigerant is 5% by mass or less, and more preferably 3% by mass or less, based on the total amount of linear organopolysiloxanes. If the amount of linear organopolysiloxanes in which n is 16 or greater exceeds the upper limit, the flash point of the refrigerant will increase, but this is not preferred because the viscosity will increase in the low-temperature range. There is no particular restriction on the lower limit, and the closer to 0% by mass the better, but for example, it is 0.01% by mass or greater, preferably 0.1% by mass or greater. 0% by mass is particularly preferred.

[0014] Furthermore, in the present invention, the refrigerant contains a compound represented by the following formula (2): [ka] (where m is an integer between 3 and 6) The amount of the cyclic polysiloxane represented by formula (2) is less than 1 part by mass, preferably 0.5 parts by mass or less, and more preferably 0.1 parts by mass or less, per 100 parts by mass of the linear organopolysiloxane. There is no particular restriction on the lower limit, and the closer to 0 parts by mass the better, with 0 parts by mass being particularly preferred. The cyclic polysiloxane represented by formula (2) is derived from a cyclic polysiloxane compound, which is a raw material for the linear organopolysiloxane. Because the cyclic polysiloxane compound is volatile, containing more than the upper limit in the refrigerant is undesirable because it lowers the flash point of the refrigerant.

[0015] In the present invention, the value of n was measured under the following conditions: 29 This was determined from Si-NMR spectra. [Measurement conditions] Measurement solvent: deuterated chloroform Sample concentration: 30% by mass Relaxation Reagent: Chromium(III) Acetylacetonate Accumulation count: 2000 times Device name: JNM-ECX-500II (manufactured by JEOL Ltd.)

[0016] The amount of the organopolysiloxane component represented by the formula (1) where n is 5 or less, the amount of the organopolysiloxane component represented by the formula (1) where n is 16 or more, and the amount of the cyclic polysiloxane represented by the formula (2) were measured by gas chromatography under the following conditions. [Measurement conditions] Equipment: Shimadzu Gas Chromatograph Nexis GC-2030 Carrier gas: Helium Flow rate: 0.6mL / min Detector: Flame ionization detector (FID) Detector temperature: 320℃ Column: DB-5MS (inner diameter 0.53 mmφ x length 30 m, packing material: silica) (Agilent Technologies) Column temperature: 50 → 280 °C (heating rate: 10 °C / min) Sample injection volume: 1.0 μL Internal standard: n-tetradecane

[0017] The organopolysiloxane of the present invention can be produced by commonly known methods, such as cohydrolysis of trimethylchlorosilane and dimethyldichlorosilane, or equilibration reaction of hexamethyldisiloxane with a cyclic polysiloxane compound such as octamethylcyclotetrasiloxane or decamethylcyclopentasiloxane in the presence of an acid or base catalyst.

[0018] Catalysts for the equilibration reaction include acidic catalysts such as sulfuric acid, fuming sulfuric acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid, and hydrochloric acid, as well as metal hydroxides such as sodium hydroxide and potassium hydroxide, and basic catalysts such as the reaction product of dimethylsiloxane and an alkali metal. The amount of catalyst added is 0.01% to 5% of the polysiloxane raw material, and the reaction temperature is generally 0°C to 100°C for acidic catalysts and 100°C to 180°C for basic catalysts.

[0019] The polysiloxane obtained by cohydrolysis or equilibration reaction is washed with water or neutralized with a neutralizing agent to remove by-product acids and catalytic acids or bases, and then subjected to a distillation process to remove low and high molecular weight components, thereby obtaining the organopolysiloxane of the present invention. The distillation process is preferably carried out under reduced pressure at a temperature of 120°C to 220°C.

[0020] The linear organopolysiloxane of the present invention must have a kinematic viscosity of 100 mm at -60°C in order to be used as a refrigerant for a cooling device. 2 / s or less, and 50 to 100 mm 2 / s, preferably 50 to 70 mm 2 / s. Kinematic viscosity at -60°C is 100mm 2 If the speed exceeds / s, the load on the circulation pump will increase. In the present invention, the kinematic viscosity at temperatures below 0°C, for example, at -20°C, -40°C, and -60°C, is a value measured using a rheometer in an environmental test chamber cooled with liquid nitrogen under the following conditions. [Measurement conditions] Equipment: DHR-2, environmental test chamber (manufactured by TA Instruments) Shear rate::1,000s -1 Plate: Aluminum parallel plate (upper diameter 25 mm, lower diameter 40 mm, gap 0.5 mm) The absolute viscosity obtained as a measurement result was converted to kinematic viscosity using the following formula (a) from the absolute viscosity and specific gravity at the measurement temperature T°C. The specific gravity (T°C) at the measurement temperature T°C was calculated using the following formula (b). Kinematic viscosity (T℃) = Absolute viscosity (T℃) / Specific gravity (T℃) Formula (a) Specific gravity (T℃)=0.0009×(25-T)+specific gravity (25℃) Formula (b)

[0021] It is desirable that the flash point of the refrigerant be higher than the temperature at which it is used. The linear organopolysiloxane of the present invention preferably has a flash point of 150°C or higher, more preferably 155°C to 260°C. In the present invention, the flash point is a value measured using a Cleveland open-type refrigerant in accordance with JIS K2265-4:2007.

[0022] The refrigerant of the present invention can be suitably used as a refrigerant for a cooling device having a mechanism for forced circulation of the refrigerant, such as a refrigerant storage tank, a refrigerant circulation device, a refrigerator for cooling the refrigerant, or a commonly known cooling device having a mechanism for forced circulation of the refrigerant using a heat exchanger. [Example]

[0023] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0024] [Example 1] A reaction vessel was charged with hexamethyldisiloxane (180 g) and decamethylcyclopentasiloxane (820 g), and under a nitrogen atmosphere, 97% sulfuric acid (30 g) was added as an acid catalyst and stirred at 25-30°C for 4 hours, followed by the addition of ion-exchanged water (13 g) and stirring at 25-30°C for 30 minutes. After separating the waste acid, the mixture was washed with water and neutralized. The mixture was heated under reduced pressure to 120-220°C, and distilled while checking the composition by gas chromatography, yielding a colorless, transparent organopolysiloxane (750 g). The resulting organopolysiloxane is represented by the above formula (1), and R 1 were all methyl groups, and the average value of n in formula (1) was 9. Furthermore, the content of organopolysiloxanes represented by formula (1) above, in which the value of n was 9, was the highest relative to the total amount of organopolysiloxanes obtained, accounting for 20 mass % of the total amount of organopolysiloxanes.

[0025] [Comparative Example 1] A reaction vessel was charged with hexamethyldisiloxane (180g) and decamethylcyclopentasiloxane (800g). Under a nitrogen atmosphere, 97% sulfuric acid (30g) was added as an acid catalyst and stirred at 25-30°C for 4 hours. Deionized water (13g) was then added and stirred at 25-30°C for 30 minutes. After separating the waste acid, the mixture was washed with water and neutralized. The mixture was heated under reduced pressure at 100-120°C, and low molecular weight components were removed by stripping, yielding a colorless, transparent dimethylpolysiloxane (780g). The resulting organopolysiloxane is represented by the above formula (1), and R 1 were all methyl groups, and the average value of n in formula (1) was 7. Furthermore, the organopolysiloxane represented by formula (1) in which the value of n was 6 had the highest content relative to the total amount of the obtained organopolysiloxane, accounting for 14 mass% of the total amount of organopolysiloxane.

[0026] Comparative Example 2 As a comparative component, commercially available dimethylpolysiloxane (kinematic viscosity 5 mm at 25 °C) was used. 2 The organopolysiloxane used was an organopolysiloxane represented by the above formula (1), R 1 are all methyl groups, and the average value of n in formula (1) is 7. Furthermore, the content of organopolysiloxanes represented by formula (1) above, where the value of n is 6, was the highest relative to the total amount of organopolysiloxanes, accounting for 16 mass % of the total amount of organopolysiloxanes.

[0027] Table 1 shows the properties of the organopolysiloxanes of the Examples and Comparative Examples. The kinematic viscosities at 20°C, 25°C, 50°C, and 100°C were measured using a Cannon-Fenske viscometer according to the method described in JIS Z8803:2011. The kinematic viscosities at 0°C, -20°C, -40°C, and -60°C were measured using a rotational rheometer according to the measurement conditions described above. The flash point was measured by a Cleveland open-type method in accordance with JIS K2265-4:2007. The mass (%) of the organopolysiloxane component represented by formula (1) where n is 5 or less relative to the total mass of organopolysiloxane, the mass (%) of the organopolysiloxane component represented by formula (1) where n is 16 or more relative to the total mass of organopolysiloxane, and the content (%) of the cyclic polysiloxane represented by formula (2) relative to the total mass of organopolysiloxane were measured by gas chromatography according to the measurement conditions described above.

[0028] [Table 1]

[0029] As described above, the organopolysiloxane of the present invention has a high flash point of 150° C. or higher while maintaining low viscosity and fluidity at low temperatures. Therefore, refrigerants containing this organopolysiloxane can be suitably used as refrigerant oils in cooling devices having a mechanism for forced refrigerant circulation.

Claims

1. A refrigerant containing a linear organopolysiloxane represented by the following formula (1): 【Chemistry 1】 (Here, R １ are each independently a methyl group or a hydroxyl group, and n is an integer of 1 to 30. the amount of the linear organopolysiloxane represented by formula (1) in which n is 5 or less is 15 mass% or less based on the total mass of the linear organopolysiloxanes, the amount of the linear organopolysiloxane represented by formula (1) in which n is 16 or more is 5 mass% or less based on the total mass of the linear organopolysiloxanes, and, The refrigerant contains a compound represented by the following formula (2): 【Chemistry 2】 (where m is an integer from 3 to 6) The amount of the cyclic polysiloxane represented by the formula (I) is less than 1 part by mass per 100 parts by mass of the linear organopolysiloxane. The refrigerant.

2. 2. The refrigerant according to claim 1, wherein the amount of the linear organopolysiloxane represented by formula (1) where n is an integer of 6 to 15 is more than 80% by mass based on the total mass of the linear organopolysiloxane.

3. 2. The refrigerant according to claim 1, wherein the linear organopolysiloxane has a flash point of 150°C or higher.

4. The linear organopolysiloxane has a flash point of 150°C or higher and a kinematic viscosity of 100mm at -60°C. ２ 10. The refrigerant of claim 1 having a refrigerant mass per square meter (m / s) or less.

5. The refrigerant according to any one of claims 1 to 4, which is a refrigerant for a cooling device.

6. The refrigerant according to claim 5, wherein the cooling device has a mechanism for forced circulation of the refrigerant.

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